1. Field of the Invention
The present invention relates to image forming device and image forming methods which are capable of handling paper fingerprint information.
2. Description of the Related Art
As one example of technology that prevents the falsification of paper documents, there exists technology that uses paper fingerprint data as information to identify individual sheet of paper. Paper sheet is composed of fine intertwined natural fibers; the intertwined configuration of these natural fibers is random, and the possibility of the existence of more than one paper sheet having the exact same fiber pattern is thought to be extremely low. Consequently, these paper fiber patterns can be used as paper fingerprint data. Similar to the fingerprints of human beings, this paper fingerprint data has the characteristic of being different for every single sheet of paper. In addition, paper fiber patterns are durable and do not break apart even when bent to some degree. The paper fiber patterns also exhibit little change as time passes. For these reasons, paper fingerprint data may be used as information to identify individual sheets of paper over a long period of time. As a method for guaranteeing a document as an original using paper fingerprint data, Japanese Patent Laid-Open No. 2004-151833 describes a method wherein paper fingerprint data of an original document is converted into a two-dimensional code, barcode, or similar codes, and the code is then printed on the original document.
In the method described in Japanese Patent Laid-Open No. 2004-151833, a user uses a scanner to scan the paper fingerprint data corresponding to the paper sheet of the original document. Next, the user needs to load the paper sheet into a printing device, and needs to issue instructions to print the code which represents the paper fingerprint data on the paper sheet. This is a highly cumbersome procedure for the user. Furthermore, for improving detection accuracy of the paper fingerprint data, care needs to be taken so that characters or other figures are not printed on the area of the paper where the paper fingerprint data was scanned. For that reason, it is necessary for the user to exercise care even in paper sheet arrangement when loading the paper sheet into the printing device. Meanwhile, there are also cases where the time required to convert the paper fingerprint data into code data is longer than the time elapsed between the start of scanning the paper fingerprint data and the start of printing. In other words, when the paper sheet is transported at a normal transport speed for printing, there are cases in which the processing that converts the paper fingerprint data into code data has not been completed by the time of the start of printing. In cases such as these, there arises the problem that the code cannot be printed on the paper sheet. If the paper sheet transport speed is slowed to avoid this problem, there arises another problem that printing performance is significantly degraded.